[ViewEngine] Add support for Thymeleaf 3 #563
Description
Between all of the view engines you support, adding something like Thymeleaf 3 (which is asynchronously processing its views) and uses "real HTML" templates would really stand up.
It could be shipped(?) with a few default dialects like the Layout dialect (which is great for injecting single views into a complete layout, which is resolved on the fly), maybe the Java 8 time dialect or similar ones.
The Thymeleaf docs are pretty helpful, and you can load files directly from the class path or the file system.